The present invention relates to an ink for ink jet recording and an ink jet recording method.
By employing the ink jet recording system, it is possible to easily and conveniently produce images at low cost. Further, along with recent improvement in image quality, it has received attention as a technique which enables high image quality recording which is sufficiently applicable to various printing fields.
However, based on the printing system, ink compositions for ink jet recording are commonly comprised of low viscosity ink compositions comprising water based solvents or non-water based solvents as a major component. Therefore, required as recording media are those which are ink absorptive. In addition, in order to achieve high image quality, special paper is required.
On the other hand, proposed as ink compositions capable of being printed onto non-ink absorptive recording media such as film and metal, based on adhesion, are, for example, an ink composition described in Japanese Patent Application Open to Public Inspection (JP-A) No. 3-216379 which is comprised of components which are polymerized by ultraviolet radiation exposure, and an ultraviolet radiation curable ink composition comprising colorants, ultraviolet radiation curing agents, and photopolymerization initiators described in U.S. Pat. No. 5,623,001.
Further, almost all of the inks for ink jet recording are commonly highly transparent inks which are mainly employed for printing onto white based recording media. Therefore, when printed onto, for example, transparent base materials employed in soft packaging and low lightness base materials, neither the desired contrast nor bright color is obtained, whereby it becomes difficult to present images with desired visibility.
In the case of poor visibility, methods are known in which visibility is achieved employing white ink with high covering properties. Proposed as white ink compositions are, for example, a white ink composition described in JP-A No. 2-45663, which is comprised of white inorganic pigments, organic solvents, and binding resins and has a viscosity of 1 to 15 cp from 5 to 40° C., and an ink composition for photocurable ink jet recording, described in JP-A No. 2000-336295, which is comprised of titanium oxide, polymerizable compounds, photopolymerization initiators, and water based solvents.
However, when these inks are applied onto non-ink absorptive recording media, ejected ink droplets spread due to their low viscosity at room temperature. Further, since these inks are comprised of solvents, thermal drying is required to remove the residue, whereby they are not suitable for printing onto thermally shrinkable base materials.
In ink jet recording, in order to achieve high resolution as well as high image quality, it is preferable to obtain multi-density levels. Known as such means are a method in which a plurality of inks of the same color at different densities is employed in combination and by modulating dot diameter, recording dots themselves are multi-valued and a method in which binary image data are subjected to halftone processing, employing an error diffusion method or a dither method so that the visible effect is as if there is a difference in density.
Further, almost all inks for ink jet recording are commonly high transparent inks which are mainly employed for printing onto white based recording media. Therefore, when printed onto, for example, transparent base materials employed in soft packaging and low lightness base materials, bright color formation is not obtained due to the absence of contrast. Ink visibility in the low density area is especially, degraded, whereby it becomes difficult to achieve high quality images.
The foregoing are desired to be resolved.